This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Casual sexual behavior among college students remains highly prevalent despite efforts to educate young adults about its risks. Students who practice casual sexual behavior place themselves at risk for sexually transmitted infections, unwanted pregnancy, and negative emotional and psychological consequences. Previous evidence has suggested that the practice of other risky behaviors such as heavy drinking is affected by norm misperception, the overestimation of the degree to which peers approve of heavy drinking and the frequency with which they practice it. Research has also yielded evidence supporting the reduction of problematic drinking through norm education campaigns geared to reduce norm overestimation. Recent studies indicate that students also overestimate the degree to which their peers approve of and engage in hooking up. The primary purpose of this longitudinal pilot investigation is to develop a similar norms-based intervention to reduce casual sexual behavior (hooking up) among college students. Participants in this study will receive normative information regarding the degree to which their peers approve of and engage in hooking up. They will then participate in three waves of data collection devised to track hook up-related attitudinal and behavioral changes longitudinally.